Determination of catecholamihes and their metabolites in body fluids such as urine ,plasma and serum is one of the most important ways to evaluate the activity of the sympathetic nervous system and support the diagnosis of many diseases in clinical medicine field. Potential cycling in the range from -0.2 - +1.2 V is used to electrodeposition of hydrous iridium oxide films onto screen printed electrode from a saturated solution of alkaline iridium (III) solution. The iridium oxide redox couple shows stable and an obvious reversible redox, with the formal potential being pH dependent in the range 1-14. The properties, stability and electrochemical properties of iridium oxide films were investigated by cyclic voltammetry. The modified electrode showed excellent catalytic activity toward oxidation of neurotransmitters (catecholamines) over a wide pll range (2-8).The electrocatalytic behavior is further exploited as a sensitive detection scheme for adrenaline and dopamine by hydrodynamic amperometry. Under the optimized conditions the calibration curves are linear in th Doncentration range 0.1- 70 and 0.l-I5UM for dopamine and adrenaline determination respectcy. The detection limit and sensitivity is 30 nM and 30 nAJEM for adrenaline and 15 and 80 nAJ[IM for dopamine. Finally the analytical performance of the modified electrode was demonstrated for the elimination of the interference by uric acid in catecholamines determ iation when present in a 1000 fold concentration excess.
